The process of adding carbonic acid to a freshly fermented beer has been known since at least 1892. In U.S. Pat. No. 475,853, issued to C. Feigenspan on May 31, 1892, there is described therein a method for carbonating beer. The document describes a process where a volume of freshly fermented beer in a closed cask is circulated by a pump along a pipe circuit. A carbonic acid injector is mounted in the pipe circuit for injecting carbonic acid in the beer. The purpose of adding carbonic acid to beer was to produce a superior quality beer. Complete saturation of the beer in the cask with carbonic acid was obtained in a period of two hours or less, thereby establishing a “time factor” in a beer carbonation recipe. The pressure inside the cask at the saturation level reached ten to twelve pounds per square inch, thereby establishing a “finish pressure factor” in a beer carbonation recipe.
It has been until 1946 before beer makers recognized that temperature was also a critical factor in the carbonation of beer. U.S. Pat. No. 2,408,439 issued to R. Muehlhofer on Oct. 1, 1946, teaches that the beer temperature for carbonation is best between 36 to 38° F. A cooling coil in the lower portion of the beer tank and a thermostat valve were provided for maintaining beer at that temperature.
A few years later, U.S. Pat. No. 2,514,463 issued to G. W. Bayers, Jr., on Jul. 11, 1950, disclosed that a carbonation process is best carried out when the beer temperature is at 34° F. A number of additional publications have emphasized the use of temperature sensors and cooling systems to maintain the beverage at a low temperature during a carbonation process. The following documents disclose different systems using either a temperature monitoring or controlling devices or both during a beverage carbonation process.    U.S. Pat. No. 3,780,198 issued to L. F. Pahl et al., on Dec. 18, 1973;    U.S. Pat. No. 4,022,119 issued to F. A. Karr on May 10, 1977;    U.S. Pat. No. 5,124,088 issued to W. C. Stumphauzer, on Jun. 23, 1992;    U.S. Pat. No. 5,704,276 issued to Y. Osajima et al., on Jan. 6, 1998.
As understood from the above documents, the prior art before 1971 have taught of three critical factors in a beer carbonation process: “process duration”; “finish pressure” and “a cool temperature”. A fourth and fifth critical factors have been taught in U.S. Pat. No. 3,578,295 issued to J. L. Hudson, on May 11, 1971. Hudson teaches that “there are four principle factors in carbonating water: (1) agitation or the mixing of water and gas by stirring the water in the gas atmosphere; (2) the pressure of the gas within the receptacle; (3) the temperature of the liquid, such as water, to be saturated with gas, since cold water has a strong affinity for absorbing carbon dioxide gas; and (4) the length of time during which carbonation is carried out”. Hudson also used a carbonation ratio of 3 to 4 volumes of gas to one volume of beverage.
A few years later, it has been recognized that a relation between the pressure of CO2 entering the carbonation receptacle and the temperature of the beverage to be carbonated is also an important factor in a beer carbonating process. In that respect, both publications listed below recognized that a pressure/temperature relation must be precisely controlled to obtain repeatability in beer taste and quality. These publications are:    U.S. Pat. No. 5,178,799 issued to J. Brown et al., on Jan. 12, 1993; and    US Publication 2003/0000971 by T. L Nielson on Jan. 2, 2003.
A number of additional documents have been found in the prior art describing different advances in processes and equipment for carbonating beverages. These documents are listed below for reference purposes to demonstrate the evolution and the state of the art in the field of beverage carbonation.    U.S. Pat. No. 608,744, issued to J. L. Alberger on Aug. 9, 1899;    U.S. Pat. No. 1,261,294, issued to M. V. Ritchey on Apr. 2, 1918;    U.S. Pat. No. 1,945,489 issued to J. R. Manley on Jan. 30, 1934;    U.S. Pat. No. 2,580,516 issued to W. L. Chapplow on Jan. 1, 1952;    U.S. Pat. No. 2,926,087 issued to F. O. Rickers on Feb. 23, 1960;    U.S. Pat. No. 3,687,684 issued to R. L. Wentworth et al., on Aug. 29, 1972;    U.S. Pat. No. 3,992,493 issued to D. D. Whyte et al., on Nov. 16, 1976;    U.S. Pat. No. 4,265,376 issued to S. S. Skidell on May 5, 1981;    U.S. Pat. No. 4,999,140 issued to A. J. Sutherland et al., on Mar. 12, 1991;    U.S. Pat. No. 5,231,851 issued to B. Adolfsson on Aug. 3, 1993;    U.S. Pat. No. 5,518,666 issued to G. Plester et al., on May 21, 1996;    U.S. Pat. No. 5,531,254 issued to A. Rosenbach on Jul. 2, 1996;    U.S. Pat. No. 9,107,448 issued to N. Giardino et al., on Aug. 18, 2015;    U.S. Pat. No. 9,107,449 issued to D. K. Njaastad et al., on Aug. 18, 2015;    DE Patent 10 2008 056 795 issued to A. Hofmann on May 27, 2010.
In short, the prior art teaches or mentions the following important factors to be considered in a beverage carbonation process:
(1) the agitation or the mixing of water and gas;
(2) the pressure of the gas within the carbonation receptacle;
(3) the temperature of the liquid to be saturated with gas;
(4) the length of time, or the inflow of gas during the carbonation phase;
(5) the pressure gradient during the carbonation phase;
(6) the volume ratio between volume of CO2/volume of liquid;
(7) the pressure/temperature ratio during the carbonation phase;
(8) the finish pressure of the carbonated beverage.
Based on the above factors, beer brewers have developed a general carbonation guide for different type of beers, as illustrated in the accompanying FIG. 1. This guide provides a volume of gas to be absorbed by a volume of beer at a specific temperature and pressure, to obtain a specific style of beer. Although this general carbonation guide is well known, individual brewers have developed their own recipes to produce and reproduce particular brands of beer and different flavors within each brand. Each flavor is distinguishable by the basic cereal with which it is produced. Each flavor is also distinguishable by its CO2 content and by the way the carbonating process is being carried out.
Referring to FIG. 2 in the attached drawings, each beer flavor is distinguishable by a CO2 pressure/flow gradient during the carbonating phase and by the final or finish pressure of the beer of a specific flavor. These flavor recipe curves are developed by brewers and are normally kept as trade secrets.
It will be appreciated that these flavor recipe curves are indirectly dependent on temperature, as a pressure/temperature relation is perhaps the most important factor in the affinity of a beer for absorbing carbon dioxide gas.
In the prior art, the temperature sensors have been mounted inside the beverage tank, near the top of the tank; near the wall of the tank, or outside the tank in a beverage recirculating pipe. Because the temperature of a fluid varies substantially within a same container, the methods to measure temperature as taught in the prior art are not considered sufficiently accurate, given that this measurement is detrimental to the success and repeatability of a beer flavor recipe. The placement of a temperature probe near the top of a tank, for example, is done with the assumption that the entire content of the tank is at a same temperature.
Beer temperature inside a carbonation tank can vary a few degrees, whether the sensor is placed at the top, the middle or at the bottom of the tank. Beer temperature also varies from near the wall of the tank to a region near the point of entry of the CO2 into the tank and the point of mixing of CO2 into the beverage. Beer temperature is also depending upon many factors such as heat transfer through the tank wall, the heat generated by pumping equipment, heat transfer through pipe insulation, etc.
As it is mentioned in U.S. Pat. No. 5,178,799 issued to Brown et al., on Jan. 12, 1993, when beverage temperature increases, the pressure in the CO2 supply line must also be increased to maintain the same carbonation level. Beverage temperature varies due to daily, seasonal, or geographic trends, and can cause excessive levels of carbonation resulting in excess carbonation, high foaming levels and wastage during bottling. Similarly, the under-carbonation of a volume of beer causes product returns due to shortfalls in client's expectations.
While the measurement and control of flow, time and pressure can be easily done precisely with modern instruments, temperature remains elusive within a same volume of beverage. In order to maintain a volume of beverage at an exact temperature for a period of time, the beverage container and the cooling equipment needs to be operated for an extended period of time after filling, to ensure that all components of that system are at a same temperature. Furthermore, the beverage itself needs to be acclimated to the reservoir and circulated entirely for an extended period of time to ensure an homogenous temperature throughout the beverage.
Furthermore, the maintaining of a volume of beverage at the same temperature also requires that the CO2 dispersed into the beverage be dissipated at the same temperature as the beverage to be treated. Such a procedure requires sophisticated equipment and a complex installation. Such a procedure lengthens the carbonation process. This equipment and installation are not always suitable to a micro-brewery where profit margins are modest.
Therefore, it is believed that there is a need in the craft brewing industry for a better system and a better method for precisely and economically monitoring beer temperature during a beer carbonation process. There is a need in the micro-brewery field for an economical system and method to precisely control a pressure/temperature ratio so that beer flavor is accurately repeatable and beer quality is as good as the product of large breweries.
In another aspect of beer carbonation, it is generally known that micro-breweries prefer to operate their processes at low pressure of less than 15 psi. A low pressure system is not subject to stringent regulations, worker qualification and re-qualification and frequent safety inspections and audits. Therefore, it is also believed that there is a need in this field for a carbonation process that can be carried out at low pressure.